The suspect arrested in Rome, who was named as Somali-born UK citizen Hussain Osman, 27, will be questioned over the bomb attempt at Shepherd's Bush station.

He had been staying with his brother, who was also taken into custody, Italian officials said.

Also on Friday, UK police arrested a third man in Notting Hill, west London, and two women at the city's Liverpool Street station.

The as yet unnamed man, arrested in Tavistock Crescent, is said by police to be of significant interest in relation to the events of 21 July.

The suspect detained last Wednesday in Birmingham was Yassin Hassan Omar, 24, who is being questioned over a bomb attempt on the Tube near Warren Street.

'I'm scared'

One man was arrested following the Notting Hill raid

BBC security correspondent Frank Gardner said police may have been able to make their arrests following tip-offs from the public or informants; electronic interception; or the questioning of people who were already in custody.

"I understand that the questioning of those people they have in custody was very productive," he said.

Our correspondent added that following Friday's arrests, the immediate priority for police was to establish if there were any further bomb plots.

Also, officers would want to know if there were any explosives lying around in warehouses and who these detainees knew.